1. Field of the Invention
The present invention relates to fluid handling and particularly to the delivery of fluid from a source to a plurality of fluid consuming loads in a predetermined sequence. More specifically, this invention is directed to distributing valves operable to sequentially deliver a fluid under pressure from a source to one or more discharge or distribution lines. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in their utility, fluid control devices of the general type to which the present invention relates have been found to be particularly useful in irrigation systems. In such systems it is often desired to supply water from a single source in sequence to a number of distribution lines; each of the distribution lines typically including a plurality of sprinkler heads. Such systems require at least one sequential distributing valve which is operable to connect the source to the distribution lines in a predetermined sequence; the distribution lines typically being supplied in individual fashion.
Sequencing valves for use in the above briefly described irrigation systems, as well as in numerous other environments, are well known in the art. However, as will be described briefly below, all previously available sequencing valves have been characterized by a number of inherent operational deficiencies. Certain of these deficiencies have characterized the sequencing valves designed in accordance with each of the several technical approaches to providing flow switching which have been followed.
As noted immediately above, prior art sequencing valves have embodied a number of different technical approaches. Thus, by way of example, a plurality of electrically or hydraulically operated remotely controlled valves have been proposed and in some cases utilized. As employed in this brief discussion of the prior art, a remotely hydraulically controlled valve is a device which is operated in response to a control signal delivered via a hydraulic line which is separate from the main fluid flow path or via an electrical cable. While possessed of a number of other significant disadvantages, the remotely operated valves of the prior art also share two principal deficiencies with all other prior art sequencing valves. These deficiencies are excessive system cost due to the necessity of employing a plurality of valves and a corresponding lack of system reliability resulting from the comparatively large total number of moving parts employed in a system.
Another approach to the design of a successful sequencing valve has been embodied in solenoid operated devices. Although directly operated solenoid controlled sequencing valves have been proposed, such valves have not been used extensively due to their high cost, limited utility and lack of reliability. Thus, by way of example, direct operated solenoid controlled sequencing valves are not suitable for use with a completely automatic pump fed distribution system unless a separate timer is employed to turn on the pump. Solenoid controlled directly operated sequencing valves are also characterized by high pressure loss and high electrical power requirements.
Another approach to the provision of a sequencing flow control resides in the flow meter operated type valve. Flow meter operated valves meter the same amount of flow to each distribution circuit regardless of the individual circuit requirements and are not adjustable for cycle time other than by increasing the number of complete cycles. Also, the valve sealing element is subject to wear due to a sliding contact. Flow meter operated valves also require a single station timer for fully automatic operation and such valves are characterized by a relatively high pressure loss. Additionally, flow meter operated valves are overly complex and subject to contamination damage.
The technical approach to sequencing valve design which has resulted in the prior art devices which have achieved the widest acceptance contemplates that the valve discharge port switching function be controlled by pulsing the flow from the fluid source. Such flow operated sequencing valves have employed ball-type valves, as exemplified by H. Davis U.S. Pat. No. 3,472,265, and rotary-axially movable valve elements, as exemplified by the cam operated device of E. Haggard U.S. Pat. No. 3,369,565. While the Haggard patent discloses a sequencing valve having an integrally mounted solenoid operated pilot valve, it will be obvious to those skilled in the art that the sequencing valve of U.S. Pat. No. 3,369,565 can operate in response to supply fluid pulses delivered to the valve inlet as a result of the operation of a suitable control device located at the source of the fluid to be distributed.
As noted above, all previous flow operated sequencing valves have been characterized by several inherent deficiencies. Perhaps the most significant of these deficiencies has been an inability of the prior art devices to operate over a wide flow range; this deficiency preventing the adaptation of a single valve to a variety of applications. The inability to operate over a wide flow range has typically been evidenced as a failure of the valve to cycle at low flow rates. There have been a number of attempts made to provide a sequencing valve which are cycle at low flow rates. The prior attempts to obtain low flow rate cycling are exemplified by the valve disclosed in U.S. Pat. No. 3,524,470 to C. Kah, Jr. The device of U.S. Pat. No. 3,524,470 incorporates flap valves in the valving member and, while this technique reduces the flow required to cycle, thus inherently offers substantial area for leakage around the valving member which establishes the minimum flow rate required to cycle. Additionally, the valve of U.S. Pat. No. 3,524,470 exhibits a narrow operational flow range if a unreasonable pressure loss is to be maintained.
Thus, to summarize the above, in previously available flow operated sequencing valves, significant flow has been required for valve operation since the pressure drop across the valve element is used to generate the force required for cycling. Obviously, if a reasonable pressure drop at high flow rates is to be maintained, a large port area in the valve element must be provided and the flow rate through this port area and around the outer diameter of the valve element must be significant to generate an adequate pressure differential to achieve cycling. Accordingly, prior art flow operated sequencing valves have been characterized by a compromise between a high pressure drop and an extremely large valve structure.
The second most significant deficiency of all prior art sequencing valves, including those briefly discussed above, is the water hammer effect created as the valves are cycled. The possible detrimental effects of water hammer to the valve itself and other components of the fluid distribution system are well known and will not be discussed herein. Water hammer has resulted because, prior to complete cycling, all of the outlet ports are exposed to the inlet thereby providing very low resistance to flow and consequently a high flow rate. When the valve element is seated the resistance to flow is reduced to that of a single flow circuit and the total flow is suddenly reduced thus producing water hammer.
A further disadvantage of prior art flow operated sequencing valves resides in the susceptability of the previous devices to jamming failure resulting from contamination. In many installations sand or other contaminates may enter the system and these contaminates may wedge between close fitting parts, such as the valving member and housing, thereby causing improper operation; this being a particular problem in the typical prior art device wherein such close fitting parts are exposed to the flow stream through the sequencing valve. The lack of reliability of prior art flow operated sequencing valves resulting from their susceptability to contamination has been aggravated by the fact that the devices have employed a comparatively large number of moving parts. Prior art flow operated sequencing valves have been further characterized by delay in or failure to cycle as a result of back flow from elevated outlet circuits. The typical prior art solution to the "back flow" problem has been to incorporate check valves in the elevated circuits and this, of course, has added to the expense and complexity of the entire distribution system.